MULTICELLULAR ORGANISMS
Section 2b – Plant Meristems
Re-Cap
• Can you name the
following cells:
• Can you describe
their functions
Learning Outcomes
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Today we will learn:
- the sites of growth in a plant
- the importance of meristems
- the way that cells specialise in plants
Plant vs. animal growth
How is the growth of plants different to the growth of
animals?
 Many plants can continue growing throughout their
lifetime.
 Most plant growth occurs by cell elongation, not cell
division.
 Growth in plants only occurs in certain tissues.
 Many plant cells retain the ability to differentiate into any cell type. This is why
cuttings can be used to create new plants.
How do plants grow?
Cell division only takes place in regions of the plant called meristems. These tissues are
found in the tips of the roots and shoots – they are therefore apical meristems.
meristem
Plants only get taller when cells in
meristems elongate following cell
division.
After this, cells differentiate into
their final form.
zone of
cell division
zone of
cell elongation
zone of
cell differentiation
Plant Cell differentiation
• Initially cells will
elongate
• Then they will develop a
vacuole
• - vacuolation
• Then the cells will
specialise
• - differentiation
• Xylem
• - will lose the vacuole,
and become hollow
• - will develop lignin
Animals, plants or both?
Lateral Meristems
• Some plants grow every year
- perennial
• Their stems need to thicken
to support the extra growth
• This thickening is controlled
by lateral meristems
• These cause the stem to get
wider every year
• This is seen in rings within
the stem
Cambium
• A young plant will start off
with a single band of xylem
and phloem
• Each year a new band (or ring)
of xylem will develop
• The phloem will also widen
• This allows the xylem and
phloem to reach the top of the
plant
• In between the xylem and
phloem is a region called
cambium
• Cambium is a lateral meristem
• – it produces the new xylem
and phloem cells
Re-Cap questions
• 1) What is a meristem?
• 2) Identify 2 regions of a plant which possess
an apical meristem?
• 3) State 2 differences between a xylem vessel
and a meristematic cell
• 4) Give ONE way in which growth in an animal
differs from growth in a plant